1. Field of the Invention
The present invention relates to plasma processing apparatus and method, and particularly to a plasma processing apparatus and method suitable for making surface treatment of a sample such as a semiconductor device by use of plasma.
2. Description of the Related Art
In the etching process using plasma, the processing gas is ionized to be activated for fast processing, and radio frequency (RF) biasing power is supplied to the processed sample so that the ions in the plasma can be incident perpendicularly to a sample to be processed (or a processed sample), thereby achieving high-precision etching for anisotropic shape and so on.
A plasma processing apparatus for this purpose is disclosed in U.S. Pat. No. 5,891,252, issued to Yokogawa, et al. This apparatus, as described in that document, has an air-core coil provided on the outer periphery of the outside of a vacuum vessel, and a circular conductor plate provided to oppose a wafer stage or substrate electrode within the vacuum vessel. In addition, an UHF band power supply and a first RF power supply are connected to the circular conductor plate, while a second RF power supply is connected to the wafer stage, so that an electric field of UHF band and anther electric field of frequencies different from the UHF band are superimposed and applied to the circular conductor plate. Thus, plasma is generated by use of electron cyclotron resonance due to the mutual action between the electromagnetic waves from the UHF band power supply and the magnetic field from the air-core coil. The superimposed RF voltage from the first RF power supply increases the bias voltage to the circular conductor plate so that the circular conductor plate and the plasma can be reacted to more produce activated species that contribute to the etching, and the second RF power supply connected to the wafer stage controls the energy of ions incident to the sample in the plasma.